With Mesa-9.0 glxinfo shows GLX_intel_swap_event for server glx extensions and for client glx extensions. Looking at the code, this seems to be a simple typo (and also apparently not a regression - but a bug that has been there from the beginning?)
Will attach a patch
Created attachment 68664 [details] [review]
Patching fixing bug
Thanks. I committed this fix to master.
on Feb 27, 2017 at 06:48:56.
(provided by the Example extension).